Embodiments of the invention generally relate to a control system of a rotary wing aircraft, and more particularly, to power management between a propulsor and a coaxial rotor of a helicopter.
A rotary wing aircraft with a coaxial contra-rotating rotor system may be capable of higher speeds as compared to conventional single rotor helicopters due in part to a semi-rigid coaxial rotor that allows the lift on each rotor to be biased to the advancing side for efficient enhanced speed. To still further increase airspeed, supplemental translational thrust is provided by a translational thrust system including an integrated propulsor unit with a propulsor (e.g., a propeller) oriented substantially horizontal and parallel to the aircraft longitudinal axis to provide thrust for high speed flight, where the integrated propulsor unit is tied to the same drive system as the engine(s) and rotors.
In a rotary-wing aircraft application, engine anticipation may be part of the engine control system to maintain rotor speed within a relatively narrow range in response to demanded torque from the rotary-wing aircraft rotor system. The capability of the engine control system to correctly anticipate changes in power required directly impacts rotor speed governor performance. Engine anticipation conventionally focuses on collective changes affecting main rotor power demand. On a helicopter with an integrated propulsor unit, the propulsor contributes a significant fraction of the total power required in many flight regimes, and collective-based anticipation is insufficient to adequately control rotor speed. Further control challenges can arise when a clutch mechanism is used to engage and disengage the propulsor of the integrated propulsor unit.
Therefore, a need exists for an improved control for engine anticipation for propulsor loads on a helicopter.